The present invention relates to electrical receptacles with interlocks for keeping power off the connector when it is being inserted and withdrawn, and, in particular, to devices for grasping the plug and preventing removal when power is being conveyed through the plug.
In the many applications for electrical connectors for power cables, safety is always important. An important safety consideration is removing power from the connector when it is being inserted or withdrawn. Such a precaution prevents dangerous arcing then and can reduce contact life as well. An early approach to solving this problem (U.S. Pat. No. 3,598,941) involved placing a spring loaded slider within a receptacle. Withdrawal of a plug from this special receptacle caused the slider to move thereby simultaneously operating a circuit breaker and removing power from the special receptacle. However, this receptacle made no attempt to physically disconnect power while retaining the plug engaged with the connector. Moreover, the mechanism was strictly internal and involved a modification to the conventional connector structure.
U.S. Pat. No. 4,335,286 concerns a plug/connector combination that may be locked together by a pin and hole assembly. However, this device requires using a non-standard connector and plug. U.S. Pat. No. 4,414,440 shows an interlock having moving components external to the connector. However, this interlock again makes no attempt to physically prevent plug removal when power is flowing.
Accordingly, there is a need for a device that will prevent application of power before a plug is inserted into a receptacle and will physically prevent removal of a plug from a receptacle when power is flowing through the receptacle.